Ship Design Research Articles

Utilizing Artificial Neural Network Ensembles for Ship Design Optimization to Reduce Added Wave Resistance and CO2 Emissions

Increased maritime cargo transportation has necessitated stricter management of emissions from ships. The primary source of this pollution is fuel combustion, which is influenced by factors such as a ship’s added wave resistance. Accurate estimation of this resistance during ship design is crucial for minimizing exhaust emissions. The challenge is that, at the preliminary parametric design stage, only limited geometric data about the ship is available, and the existing methods for estimating added wave resistance cannot be applied. This article presents the application of artificial neural network (ANN) ensembles for estimating added wave resistance based on dimensionless design parameters available at the preliminary design stage, such as the length-to-breadth ratio (L/B), breadth-to-draught ratio (B/T), length-to-draught ratio (L/T), block coefficient (CB), and the Froude number (Fn). Four different ANN ensembles are developed to predict this resistance using both complete sets of design characteristics (i.e., L/B, B/T, CB, and Fn) and incomplete sets, such as L/B, CB, and Fn; B/T, CB, and Fn; and L/T, CB, and Fn. This approach allows for the consideration of CO2 emissions at the parametric design stage when only limited ship dimensions are known. An example in this article demonstrates that minor modifications to typical container ship designs can significantly reduce added wave resistance, resulting in a daily reduction of up to 2.55 tons of CO2 emissions. This reduction is equivalent to the emissions produced by 778 cars per day, highlighting the environmental benefits of optimizing ship design.

Numerical analysis of coupling effect between sloshing and motion responses of a KCS in uni- and bi-directional waves

The seakeeping behaviour can be severely affected by the coupling between sloshing and ship motions in waves. The sloshing behaviour of liquid-loaded ships in bi-directional waves differs significantly from that in uni-directional waves. Given that ships operate in short-crested or multi-directional waves during their whole service period, it is significant to gain a deeper understanding of the effect of wave directionality on the coupling between sloshing and ship motions. In this study, a KRISO container ship (KCS) model with type-B liquefied natural gas (LNG) cargo tanks is adopted for coupling analysis. The 2D long-crested regular wave is adopted as an uni-directional wave, and three dimensional (3-D) cross wave is adopted as a bi-directional wave. The computational fluid dynamics (CFD) method is applied for the sloshing and seakeeping simulation of the ship model in different wave fields. The differences in wave elevation, sloshing forces, and coupling effects between ship motions and sloshing are studied in these two wave fields by adjusting control parameters such as ship heading angle and filling ratio. The comparative results indicate that sloshing behaviour and coupled motion responses in cross waves should be paid enough attention during ship design and evaluation.

Comparative Analysis on the Effect of Bow Shapes on the Ship Resistance using CFD Simulation and Model Test

Shipping companies and ship owners are very concerned with reducing operating costs. One way to achieve this is by improving the hydrodynamic performance of ships, which can reduce fuel consumption by decreasing total resistance. Optimizing ship design, particularly the bow shape, is crucial for enhancing hydrodynamic performance, fuel efficiency, and operational costs. While CFD simulations have become a powerful tool in naval architecture, their accuracy and reliability in predicting hydrodynamic resistance for different bow shapes need validation through experimental data. This study employs computational tools using Fine/Marine NUMECA and model tests carried out in a towing tank. The primary objective is to compare the hydrodynamic resistance of axe bow and conventional bow shapes. Additionally, the contributions of different resistance components (residuary and friction) to each bow shape are identified and quantified. The study concludes that the axe bow shape offers notable improvements in reducing total resistance compared to the conventional bow, providing a reduction of up to 12.5%. Moreover, the residuary resistance component has a more significant effect on total resistance compared to friction resistance.

Multi‐Objective Optimization and Experimental Research of Ship Form Based on Improved Bare‐Bones Multi‐Objective Particle Swarm Optimization Algorithm

ABSTRACTShip form optimization poses a complex and high‐dimensional engineering challenge. Therefore, when conducting multi‐objective optimization research of ship forms, traditional intelligent optimization algorithms are prone to falling into local optima solution and difficult to converge. In order to effectively improve the diversity and convergence performance of the algorithm, this paper improves the bare‐bones multi‐objective particle swarm optimization (BBMOPSO) algorithm by dynamically adjusting the local and global search step sizes, and verifies the algorithm's reliability through standard function testing. Then, a multi‐objective optimization design framework with high efficiency and high integration is constructed. Taking DTMB 5512 as the research case, Free Form Deformation (FFD) method is used for hull deformation, and the proposed algorithm is used for multi‐objective optimization of resistance performance and motion response. Ship model tests were conducted on the DTMB 5512's original hull. And the numerical simulations were compared with the ship model tests. Finally, under the constructed multi‐objective optimization design framework, satisfactory solutions were obtained through the improved algorithm, which confirms the effectiveness and practicality of the improved algorithm. The results show that the algorithm improved in this paper can provide some theoretical basis and technical support for green ship design and low‐carbon shipping.

Predicting practical ship powering and speed loss in waves using added resistance test results

ABSTRACT This paper introduces a practical technique for accurately estimating ship propulsion and speed loss in the presence of waves. Utilising the previously established self-propulsion estimation framework, our approach enhances the method, which previously solely considered bare hull resistance, propeller performance, thrust deduction factor, and wake fraction, by incorporating added resistance test results. The full-scale DTC container ship is the focus of our investigation, providing a thorough examination of its performance in different sea states. The model's predictive abilities are enhanced by incorporating test data on added ship resistance, and it addresses a crucial aspect that is generally disregarded while estimating self-propulsion. This research is considered to be a contribution to the advancement of ship hydrodynamics, as it offers a practical and reliable tool for ship designers, operators, and researchers to accurately assess powering requirements and speed loss in harsh ocean conditions.

Sustainable Ship Design and Digital Twin Yard

In an era where technological advancement and environmental consciousness are inextricably linked, the shipbuilding industry stands at a pivotal juncture [...]

Investigation on the Effect of Energy Release Rate of Aluminized Explosive on the Damage of Underwater Targets

AbstractAs a type of high‐energy explosive, aluminized explosives are extensively used in underwater weapons and ammunition. This study aims to investigate the energy release rate on the damage of underwater targets caused by aluminized explosives (RDX/Al). The ship was selected as a target, and numerical simulations were conducted using AUTODYN software to study the energy release rate corresponding to different particle sizes of aluminum powder (25 nm −300 μm) in the underwater explosion process of RDX/Al, as well as its destructive effect on targets in the water. The research quantitatively evaluates the whole ship′s destruction results, including longitudinal bending deformations and crevasse. In addition, typical cabins were selected in this study to assess the local damage effects by analyzing stress, shock wave pressure, displacement, and acceleration shock response. Based on the damage results, it was revealed that RDX/Al with aluminum powder particle sizes ranging from 54 nm to 145 nm exhibited the most optimal damaging effects on ships after underwater explosions. These findings provide a basis for improving the destructive power of aluminized explosives against underwater targets, simultaneously, they can be utilized by ship designers to guide research and development of improved protective measures, aiming to reduce the vulnerability of ships to explosive attacks.

Letting losses be lessons: Human-machine cooperation in maritime transport

Navigation safety has been a critical guarantee of global shipping, and it becomes more challenging given the increasing employment of advanced technologies and novel ship design in the era of Maritime Autonomous Surface Ships (MASS). The human-centred risk analysis of human-machine cooperation is scarce in general and emerging in maritime transport in specific. This paper aims to develop a new approach enabling the analysis of significant risk influencing factors (RIFs) in human-machine cooperation through an in-depth investigation of the occurred mistakes and violations in the cooperative operations of seafarers and machines in maritime transport. Its novelties consist of (1) a novel approach to analysing and quantifying the connectivity between humans and machines in safety-critical operations, (2) new integration of the frequency and impact of RIFs in the human-machine cooperation model, and (3) ultilisation of graph theory to generate a network to analyse critical human-machine RIFs and their interactions with the system. The connectivity analysis of RIFs is conducted through a weighted undirected network, showing the features of RIF connectivity accommodating the closed-loop system. The proposed novel approach, which combines the frequency and impact features to identify critical RIFs and analyses graphical features, will aid to realise the human-centred risk analysis for MASS. The findings make contributions for ship designers to rationalise the clustering design of function-based automation and training organisations to improve seafarer skills by rationally considering the identified risk-based human-machine cooperation features, and providing new competence schemes that can fit the demands of MASS in future.

Advanced Analysis of Marine Structures—Edition II

One of the key issues in the design of modern ship and offshore structures is the accurate prediction of strength under various load conditions, especially impact, ultimate and fatigue strength [...]

Overview of Theory, Simulation, and Experiment of the Water Exit Problem

The water exit problem, which is ubiquitous in ocean engineering, is a significant research topics in the interaction between navigators and water. The study of the water exit problem can help to improve the structural design of marine ships and underwater weapons, allowing for better strength and movement status. However, the water exit problem involves complex processes such as three-phase gas–liquid–solid coupling, cavitation, water separation, liquid surface deformation, and fragmentation, making it challenging to study. Following work carried out by many researchers on this issue, we summarize recent developments from three aspects: theoretical research, numerical simulation, and experimental results. In theoretical research, the improved von Karman model and linearized water exit model are introduced. Several classical experimental devices, data acquisition means, and cavitation approaches are introduced in the context of experimental development. Three numerical simulation methods, namely, the BEM (Boundary Element Method), VOF (Volume of Fluid), and FVM (Finite Volume Method) with LES (Large Eddy Simulation) are presented, and the respective limitations and shortcomings of these three aspects are analyzed. Finally, an outlook on future research improvements and developments of the water exit problem is provided.

Assessing the reliability of a ship energy performance simulation tool through on-board data

To mitigate the environmental impact of shipping on climate change, it is nowadays urgent to explore energy efficiency and cost-effective measures by means of reliable digital tools. These are becoming essential for assisting the design of new ships and the refurbishment of the existing ones, as well as for assessing and optimizing the energy performance of a ship during its entire life-cycle. This paper focuses on the verification of the reliability of a novel ship energy dynamic simulation tool, developed for the calculation of the energy, economic, and environmental performance of large ships, the design and optimization of energy system layouts and operational logics, as well as the definition of design and management guidelines for ships. The reliability of the developed model was verified through the use of data measured onboard an existing sample cruise ship. The verification procedure is conducted for assessing the reliability and for exploiting the potentiality of dynamic analysis for a more precise evaluation of ships energy loads, temperature levels, and necessary sizes of possible saving technologies. The validated tool will enable reaching two different goals: i) to evaluate different energy system layouts and to define the optimal one for achieving the present imposed targets and constraints, ii) to obtain a large amount of data for allowing the implementation of the digital twin approach in the maritime sector. The model validation was successfully achieved and very low or negligible deviations, lower than 4%, of numerical data vs. measurements were observed. Through the validated simulation tool approximately 23.4 GWh of primary energy from polluting fuels over two weeks is computed. In addition, the model provided insights into the flow rate, temperature levels, and energy flows of the ship energy system, necessary for identifying the amount of thermal energy to be recovered as well as potential solutions to enhance the energy efficiency of the entire system.

A novel method for evaluating ship concept performance in transport systems

Abstract Transport carries significant external costs such as climate change, accidents, pollution, and road congestion, driving national and international strategies for the development of new transport concepts. This includes shifting larger cargo volumes away from roads to more sustainable transport modes such as waterborne. The SEAMLESS project was launched in 2023 to answer to these needs by developing technology for autonomous waterborne zero-emission feeder-loop services. The realisation of such services depends on their modal competitiveness. Autonomous ships are expected to reduce transport costs and emissions, and ultimately improve logistical performance. There are, however, few published studies that quantify these impacts of autonomy. Furthermore, commercial waterborne autonomous transport services do not exist yet, limiting the possibilities for empirical analysis. Hence, research is needed to address exactly how and to what extent, autonomy improves competitiveness in different applications. This paper addresses the need for more empirical analyses of innovative waterborne transport performance, by presenting a novel method for evaluating ship concept performance in transport systems. The impacts of design choices are captured through hydrodynamic and logistical simulations. The method can be applied to transport systems consisting of both conventional and novel ship designs, operating on one or more routes including transhipments. It is implemented in the software SIMPACT and applied to a case study which establishes a shortsea feeder-loop service in the Bergen area in Norway. The Bergen municipality has decided that the container terminal is to be moved out of the city centre to reduce local traffic and emissions. However, in the absence of a competitive waterborne transport service in this region, the relocation will have the unfortunate consequence of an estimated annual net increase in regional truck traffic of 40,000 additional truck trips over 25km. By means of the proposed methodology, this paper investigates the feeder-loop concept and compare its quantified performance to truck transport and finds that competition is feasible.

Enhancing stability and performance of flexible membrane structures in wake flows through jet flow control

This study investigates jet flow control on flexible membrane structures placed in the wake of a stationary cylinder to enhance performance and stability. Flexible membranes, found in both nature and engineering, often face nonlinear disturbances where passive deformation is insufficient. Inspired by adaptive fish fins, we explore active flow control strategies using a high-fidelity fluid–structure interaction solver to simulate the dynamics of a flexible membrane downstream of a cylinder. High-momentum jet flows with different momentum coefficients are applied at membrane leading edge to modulate the boundary layer flow features. Numerical simulation results reveal that jet flow control can weaken the wake interference effect on the membrane dynamics, resulting in lift improvement and flow-induced vibration suppression. The flow separation within the boundary layer is suppressed by high-momentum jet flows, thereby enhancing lift performance and stability. The reason of the flow-induced vibration suppression is attributed to the redistribution of the vibration energy in high-order structure modes excited by jet flows. Our results demonstrate that jet control has great potential for optimizing the performance and stability of flexible membrane structures in complex flow environments, providing valuable insights into the design of next-generation intelligent underwater vehicles and ships with flexible membrane propulsion systems.

Impact of automation and zero-emission propulsion on design of small inland cargo vessels

Abstract Small inland waterways offer considerable capacity for modal shift of cargo transport. Revitalization of smaller inland waterways, however, may require new vessel designs as most of the existing small vessels are outdated and incompatible with the present state of the technology development and the current commercial and regulatory requirements. This paper investigates the possibilities for modernization of small inland vessel designs and offers a systematic analysis of impact of “automation” and “zero-emission propulsion technology” on reference designs of standard European inland cargo vessels of CEMT classes I, II, III, and IV. The adopted level of automation enables the vessels to be remotely operated without human crew onboard, whereas the adopted zero-emission propulsion concept is based on electrification of the powertrain. The paper identifies the impacts of the modernization on general arrangement, cargo capacity, safety, structural design, etc. and indicates the vessel classes which could be the most promising candidates for the design of a future small autonomous inland ships.

Automatic Optimal Design Method for Minimum Total Resistance Hull Based on Enhanced FFD Method

Hull optimization plays a crucial role in enhancing ship performance and efficiency. This study aimed to improve ship performance, particularly by reducing total resistance, through automated optimization methods. To this end, an integrated, fully automated optimization program was developed based on Python, incorporating Enhanced Free-Form Deformation (FFD) technology, scripted CFD numerical evaluation, and the Particle Swarm Optimization (PSO) algorithm. This program allowed precise control of hull form, improving efficiency while reducing costs. The KCS hull, known for its excellent resistance performance, was chosen as the optimization target, with the goal of minimizing total resistance by adjusting the bulbous bow line plan. The research results indicated that the optimized scheme exhibited lower resistance characteristics compared to the original design while satisfying design constraints. This study not only provides a new optimization strategy for ship design but also lays a foundation for future hull optimization research.

An efficient method to simulate ship self-propulsion in shallow waters and its application to optimize hull lines

Emerging environmental challenges, such as pronounced low water levels and a constantly increasing transport volume, underscore the need to address logistical complexities and to refocus attention on the performance of self-propulsion vessels in restricted and confined waters. Recognizing the demand for an accurate and efficient ship design method, we modified an actuator disk model to predict ship propulsion. This model was designed to be applicable to various kinds of ships, with special features tailored to meet the specific requirements of inland water vessels, particularly those equipped with ducted propellers. We implemented this model into the open-source CFD software library OpenFOAM to be used in conjunction with either single- or multiphase incompressible solvers. We validated this implemented model against model test data, thereby demonstrating its capability to accurately predict propulsion performance of a typical inland waterway vessel. Following validation, we employed this model in an automated optimization process, demonstrating its robust and efficient applicability for a practical user-defined case to improve a ship's afterbody lines. Meticulous grid convergence studies ensured the predictive convergence of our simulations. Our validation covered various ship speeds at three distinct water depths, ranging from a moderate water depth-to-draft ratio h/T of 2.67 to an extreme shallow water depth-to-draft ratio h/T of 1.25. We validated our simulated results against data extracted from our own previous model tests, comprising measured ship trim and ship sinkage, propeller thrust, duct thrust, propeller torque, propeller revolution rate, and propulsion power. We investigated the influence of water depth also on various parameters, such as friction and pressure distributions, free surface interactions, and velocity patterns. Finally, we integrated the developed method into an automated optimization process that we tailored for a selected test cases of the considered ship operating in water depth to draft ratios h/T of 2.67. This integrated process facilitated the systematic refinement of the ship's afterbody lines, representing a crucial step in the pursuit to enhance ship performance.

System-based ship design of a deep-sea mining vessel

ABSTRACT This paper applies the system-based ship design (SBSD) method to the conceptual design of a deep-sea mining vessel. The anticipated mine site is situated on the Norwegian extended continental shelf, where three production scenarios are assessed. The design process is documented, including a problem statement, mission description, functions, space requirements of various sub-systems, stability calculations, and preliminary cost estimates. A combination of data from existing technologies and estimates is used to set the relevant parameters, and the applicability of SBSD in the conceptual design of novel vessels is discussed. We find that when data is lacking in conceptual ship design, inspiration can be found from similar systems in established maritime industries, such as the offshore oil and gas industry.

Assessments of multiple metocean forecasts in the North Atlantic Ocean

Accurate wind and wave forecasts are crucial for a variety of marine operations, including ship design, navigation safety, and engineering. This study evaluates the predictability of wind and wave conditions in the North Atlantic Ocean using both deterministic and ensemble forecast models. A dataset of 29 deep water buoys was used to validate deterministic and ensemble forecasts from the National Centres for Environmental Prediction (NCEP), the Canadian Meteorological Centre (CMC), the European Centre for Medium-Range Weather Forecasts (ECMWF), and the German Weather Service (DWD). A comparison of deterministic and ensemble forecast performance was conducted using eight statistical metrics focusing on the significant wave heights associated with 10-m wind speed. The results indicate that ensemble models exhibit higher correlation coefficients and lower scatter root mean square error especially beyond the 7th forecast day, outperforming deterministic models. The findings suggest that ensemble forecasts offer a more reliable estimation of forecast, enhancing predictability for marine operations.

Numerical Simulation of the Unsteady Airwake of the Liaoning Carrier Based on the DDES Model Coupled with Overset Grid

The wake behind an aircraft carrier under heavy wind condition is a key concern in ship design. The Chinese Liaoning ship’s upturned bow and the island on the deck could cause serious flow separation in the landing and take-off area. The flow separation induces strong velocity gradients and intense pulsations in the flow field. In addition, the sway of the aircraft carrier caused by waves could also intensify the flow separation. The complex flow field poses a significant risk to the shipboard aircraft take-off and landing operation. Therefore, accurately predicting the wake of an aircraft carrier during wave action motion is of great interest for design optimization and recovery aircraft control. In this research, the aerodynamic around an aircraft carrier (i.e., Liaoning) was analyzed using the computational fluid dynamics technique. The validity of two turbulence models was verified through comparison with the existing data from the literature. The upturned bow take-off deck and the right-hand island were the main areas where flow separation occurred. Delayed detached eddy simulation (DDES), which combines the advantages of LES and RANS, was adopted to capture the full-scale spatial and temporal flow information. The DDES was also coupled with the overset grid to calculate the flow field characteristics under the effect of hull sway. The downwash area at 15° starboard wind became shorter when the hull was stationary, while the upwash area and turbulence intensity increased. The respective characteristics of the wake flow field in the stationary and swaying state of the ship were investigated, and the flow separation showed a clear periodic when the ship was swaying. Comprehensive analysis of the time-dependent flow characteristic of the approach line for fixed-wing naval aircraft is also presented.

Circular Economy: Research in the Maritime Domain

The maritime domain is a very broad domain encompassing ship design, construction, transportation, export–import, port management, energy, ocean, and waterways management. The assumption that the marine industry is less flexible for a transition from linear economy to circular economy (CE) is being challenged. A ship is a factory/city in motion, and therefore, CE principles may be applied to a ship. CE principles can be applied to ports, energy, and waterways management. Successful implementation of CE requires a comprehensive mapping of business models, projects, products, and services; identification of all stakeholders; and using biomimicry in manufacturing. CE can help in the regeneration and restoration of natural capital. The circular business models can help in increasing revenue, reducing costs, and saving the environment. CE can be extended to include reimagining, realigning, reworking, and reaching out to different players in the maritime domain. The marine industry faces the challenges of decarbonization and end-of-life vessel management.